1. Field of the Invention
The present invention generally relates to the field of inspection and analysis of specimens. More particularly, the present application relates to gas assisted electron beam induced etching and cross sectioning.
2. Description of Related Art
Some techniques for cross sectioning and inspecting a test sample involve destructively cleaving a test sample in order to examine various elements in the sample. Other techniques for cross sectioning a test sample involve using focused ion beams, gas assisted ion beam induced etching, and high energy electron beam induced etching. However, ion beam based etching and deposition, using gallium, causes gallium poisoning, knock-on implant contamination, and sputtering of surface material onto the substrate and adjacent surfaces in the vacuum work chamber. In many cases, inspecting the sample prevents the sample from being used in production. In other cases, scanning the sample introduces contaminants such as gallium and carbon onto the test sample that interfere with the inspection of the sample.
Consequently, it is desirable to provide improved techniques and systems for characterizing and cross sectioning test samples.
Methods and apparatus are providing for inspecting and cross sectioning a test sample. An electron beam is tuned to cause secondary electron emissions upon scanning a target area. Low reactivity substances, which are converted to elemental components with a high degree of reactivity, are introduced to etch and remove materials and impurities from the scan target. Residual components are evacuated. In one example, a laser is used to illuminate and thermally activate the area scanned by the electron beam, and to assist in the removal of residual components with poor vapor pressure.
In one embodiment, a method for inspecting a test sample is provided. A first scan target in a test sample is scanned by using an electron beam generator configured to emit particles with a first landing energy. The first landing energy causes secondary electron emissions from the first scan target. A reactive substance is introduced and a residual component is removed at the first scan target during a first period of time. The intensity of secondary electron emissions is measured during a second period of time.
In another embodiment, an apparatus for characterizing a sample is provided. The apparatus includes an electron beam generator operable to scan a first scan target in a sample using electrons with a first landing energy. The electron beam generator induces secondary electron emissions from the first scan target. A reactive substance injector is operable to introduce a reactive substance near the first scan target in order to remove carbon from the first scan target during periodic intervals. A secondary electron emission detector is configured to measure the intensity of secondary electron emissions between the periodic intervals.